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<title>CodeMirror: Version 3 upgrade guide</title>
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    <ul>
        <li><a class=active href="#upgrade">Upgrade guide</a>
        <li><a href="#dom">DOM structure</a></li>
        <li><a href="#gutters">Gutter model</a></li>
        <li><a href="#events">Event handling</a></li>
        <li><a href="#marktext">markText method arguments</a></li>
        <li><a href="#folding">Line folding</a></li>
        <li><a href="#lineclass">Line CSS classes</a></li>
        <li><a href="#positions">Position properties</a></li>
        <li><a href="#matchbrackets">Bracket matching</a></li>
        <li><a href="#modes">Mode management</a></li>
        <li><a href="#new">New features</a></li>
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<article>

    <h2 id=upgrade>Upgrading to version 3</h2>

    <p>Version 3 does not depart too much from 2.x API, and sites that use
        CodeMirror in a very simple way might be able to upgrade without
        trouble. But it does introduce a number of incompatibilities. Please
        at least skim this text before upgrading.</p>

    <p>Note that <strong>version 3 drops full support for Internet
        Explorer 7</strong>. The editor will mostly work on that browser, but
        it'll be significantly glitchy.</p>

    <section id=dom>
        <h2>DOM structure</h2>

        <p>This one is the most likely to cause problems. The internal
            structure of the editor has changed quite a lot, mostly to implement a
            new scrolling model.</p>

        <p>Editor height is now set on the outer wrapper element (CSS
            class <code>CodeMirror</code>), not on the scroller element
            (<code>CodeMirror-scroll</code>).</p>

        <p>Other nodes were moved, dropped, and added. If you have any code
            that makes assumptions about the internal DOM structure of the editor,
            you'll have to re-test it and probably update it to work with v3.</p>

        <p>See the <a href="manual.html#styling">styling section</a> of the
            manual for more information.</p>
    </section>
    <section id=gutters>
        <h2>Gutter model</h2>

        <p>In CodeMirror 2.x, there was a single gutter, and line markers
            created with <code>setMarker</code> would have to somehow coexist with
            the line numbers (if present). Version 3 allows you to specify an
            array of gutters, <a href="manual.html#option_gutters">by class
                name</a>,
            use <a href="manual.html#setGutterMarker"><code>setGutterMarker</code></a>
            to add or remove markers in individual gutters, and clear whole
            gutters
            with <a href="manual.html#clearGutter"><code>clearGutter</code></a>.
            Gutter markers are now specified as DOM nodes, rather than HTML
            snippets.</p>

        <p>The gutters no longer horizontally scrolls along with the content.
            The <code>fixedGutter</code> option was removed (since it is now the
            only behavior).</p>

        <pre data-lang="text/html">
&lt;style>
  /* Define a gutter style */
  .note-gutter { width: 3em; background: cyan; }
&lt;/style>
&lt;script>
  // Create an instance with two gutters -- line numbers and notes
  var cm = new CodeMirror(document.body, {
    gutters: ["note-gutter", "CodeMirror-linenumbers"],
    lineNumbers: true
  });
  // Add a note to line 0
  cm.setGutterMarker(0, "note-gutter", document.createTextNode("hi"));
&lt;/script>
</pre>
    </section>
    <section id=events>
        <h2>Event handling</h2>

        <p>Most of the <code>onXYZ</code> options have been removed. The same
            effect is now obtained by calling
            the <a href="manual.html#on"><code>on</code></a> method with a string
            identifying the event type. Multiple handlers can now be registered
            (and individually unregistered) for an event, and objects such as line
            handlers now also expose events. See <a href="manual.html#events">the
                full list here</a>.</p>

        <p>(The <code>onKeyEvent</code> and <code>onDragEvent</code> options,
            which act more as hooks than as event handlers, are still there in
            their old form.)</p>

        <pre data-lang="javascript">
cm.on("change", function(cm, change) {
  console.log("something changed! (" + change.origin + ")");
});
</pre>
    </section>
    <section id=marktext>
        <h2>markText method arguments</h2>

        <p>The <a href="manual.html#markText"><code>markText</code></a> method
            (which has gained some interesting new features, such as creating
            atomic and read-only spans, or replacing spans with widgets) no longer
            takes the CSS class name as a separate argument, but makes it an
            optional field in the options object instead.</p>

        <pre data-lang="javascript">
// Style first ten lines, and forbid the cursor from entering them
cm.markText({line: 0, ch: 0}, {line: 10, ch: 0}, {
  className: "magic-text",
  inclusiveLeft: true,
  atomic: true
});
</pre>
    </section>
    <section id=folding>
        <h2>Line folding</h2>

        <p>The interface for hiding lines has been
            removed. <a href="manual.html#markText"><code>markText</code></a> can
            now be used to do the same in a more flexible and powerful way.</p>

        <p>The <a href="../demo/folding.html">folding script</a> has been
            updated to use the new interface, and should now be more robust.</p>

        <pre data-lang="javascript">
// Fold a range, replacing it with the text "??"
var range = cm.markText({line: 4, ch: 2}, {line: 8, ch: 1}, {
  replacedWith: document.createTextNode("??"),
  // Auto-unfold when cursor moves into the range
  clearOnEnter: true
});
// Get notified when auto-unfolding
CodeMirror.on(range, "clear", function() {
  console.log("boom");
});
</pre>
    </section>
    <section id=lineclass>
        <h2>Line CSS classes</h2>

        <p>The <code>setLineClass</code> method has been replaced
            by <a href="manual.html#addLineClass"><code>addLineClass</code></a>
            and <a href="manual.html#removeLineClass"><code>removeLineClass</code></a>,
            which allow more modular control over the classes attached to a line.</p>

        <pre data-lang="javascript">
var marked = cm.addLineClass(10, "background", "highlighted-line");
setTimeout(function() {
  cm.removeLineClass(marked, "background", "highlighted-line");
});
</pre>
    </section>
    <section id=positions>
        <h2>Position properties</h2>

        <p>All methods that take or return objects that represent screen
            positions now use <code>{left, top, bottom, right}</code> properties
            (not always all of them) instead of the <code>{x, y, yBot}</code> used
            by some methods in v2.x.</p>

        <p>Affected methods
            are <a href="manual.html#cursorCoords"><code>cursorCoords</code></a>, <a
                    href="manual.html#charCoords"><code>charCoords</code></a>, <a href="manual.html#coordsChar"><code>coordsChar</code></a>,
            and <a href="manual.html#getScrollInfo"><code>getScrollInfo</code></a>.</p>
    </section>
    <section id=matchbrackets>
        <h2>Bracket matching no longer in core</h2>

        <p>The <a href="manual.html#addon_matchbrackets"><code>matchBrackets</code></a>
            option is no longer defined in the core editor.
            Load <code>addon/edit/matchbrackets.js</code> to enable it.</p>
    </section>
    <section id=modes>
        <h2>Mode management</h2>

        <p>The <code>CodeMirror.listModes</code>
            and <code>CodeMirror.listMIMEs</code> functions, used for listing
            defined modes, are gone. You are now encouraged to simply
            inspect <code>CodeMirror.modes</code> (mapping mode names to mode
            constructors) and <code>CodeMirror.mimeModes</code> (mapping MIME
            strings to mode specs).</p>
    </section>
    <section id=new>
        <h2>New features</h2>

        <p>Some more reasons to upgrade to version 3.</p>

        <ul>
            <li>Bi-directional text support. CodeMirror will now mostly do the
                right thing when editing Arabic or Hebrew text.
            </li>
            <li>Arbitrary line heights. Using fonts with different heights
                inside the editor (whether off by one pixel or fifty) is now
                supported and handled gracefully.
            </li>
            <li>In-line widgets. See <a href="../demo/widget.html">the demo</a>
                and <a href="manual.html#addLineWidget">the docs</a>.
            </li>
            <li>Defining custom options
                with <a href="manual.html#defineOption"><code>CodeMirror.defineOption</code></a>.
            </li>
        </ul>
    </section>
</article>

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